```LAGRANGE
           __   __             __   ___
|     /\  / _` |__)  /\  |\ | / _` |__
|___ /~~\ \__> |  \ /~~\ | \| \__> |___

```
# Help

## What is Gemini

Gemini is a simple protocol for serving content over the internet. It specifies a Markdown inspired format allowing basic plain text document markup. Compared to HTTP and HTML, Gemini is vastly simpler and easier to work with.

=> gemini://geminiprotocol.net/docs/faq.gmi Project Gemini FAQ
=> gemini://geminiprotocol.net/docs/specification.gmi Protocol and 'text/gemini' specification

## What is Lagrange

Lagrange is a cross-platform client for browsing Geminispace. It offers modern conveniences familiar from web browsers, such as smooth scrolling, inline image viewing, multiple tabs, visual themes, Unicode fonts, bookmarks, history, and page outlines.

Like Gemini, Lagrange has been designed with minimalism in mind. It depends on a small number of essential libraries. It is written in C and uses SDL for hardware-accelerated graphics. OpenSSL is used for secure communications.

=> about:lagrange            About Lagrange
=> https://www.libsdl.org/   SDL: Simple DirectMedia Layer
=> https://www.openssl.org/  OpenSSL: Cryptography and SSL/TLS Toolkit

### Features

* Beautiful typography with full Unicode support
* Autogenerated page style and symbol for each Gemini domain
* Light and dark color themes
* Smooth scrolling
* Scaling page content (50%...200%)
* Scaling factor for the UI (for arbitrary monitor DPI)
* Curses-based TUI as an alternative to the graphical interface
* Sidebars for managing bookmarks, identities and subscribed feeds, and viewing browsing history and the page outline
* Multiple tabs
* Split view for browsing two pages at once
* Persistent app state — tabs and history are restored on next run
* Configurable keybindings
* Customizable UI color palette
* Open links via keyboard shortcuts
* Select and copy text with the mouse
* Find text on the page
* Open image and audio links inline on the same page
* Instant back/forward navigation (on macOS supports swipes on trackpad)
* Subscribe to Gemini and Atom feeds
* Identity management — create and use TLS client certificates
* Smart suggestions when typing an URL — search bookmarks, history, feeds, identities
* Search engine integration
* Configurable text snippets that can be pasted in input fields and used as custom search queries
* Use Gemini pages as a source of bookmarks
* Audio playback: MP3, Ogg Vorbis, WAV
* Read Gempub books and view ZIP archive contents
* Built-in support for uploading and editing content using the Titan protocol
* Built-in support for Gopher, Finger, Spartan, Nex, Misfin, and Guppy
* Use proxy servers for Gemini, HTTP, and Gopher content

## Why not just use a web browser

Modern web browsers are complex beasts. In fact, they are so complex that one can create a fully functional virtual machine inside one and run another operating system!

=> https://win95.ajf.me Windows 95 on DOSBox (using Emscripten)

If one seeks to just read text and view images, this is absurd overkill. Having a universal platform that runs everywhere and on everything is clearly a valuable notion, but it comes with a hefty price tag. The software stack towers ever higher, and hardware needs to be ever more powerful and complicated to run it well. However, everything on the internet doesn't have to rely on this behemoth.

One way to browse Gemini content is via web browser extensions or proxies that translate the content for the web. This may be a sufficient and easy solution for you. However, native clients such as Lagrange also benefit from the simpleness of the protocol and the content. The experience can be optimized, and the software runs well even on simple hardware like the Raspberry Pi.

# 1 User interface

Lagrange's user interface is modeled after web browsers:

* There is a navigation bar at the top with Back and Forward buttons.
* There is a tab bar for switching tabs. The tab bar is hidden if there is only one tab open.
* There are sidebars for managing bookmarks, subscribed feeds, and TLS identities, and viewing history and the page outline. Sidebars are hidden by default.
* There is a search bar that appears at the bottom when searching text on a page.

Tip: Try pressing ${CTRL+}5 now to see the page outline.

The user interface has been designed for both mouse and keyboard based use. When using a mouse the most commonly needed features are available via context menus, for example by right-clicking on the currently open page. Keyboard shortcuts on the other hand can provide a very quick and fluid user experience. For example, to open the "CAPCOM" bookmark, one might use the following keyboard shortcuts:

* ${CTRL+}L to activate the URL input field
* Type "cap" which shows the "CAPCOM" bookmark as the first lookup result
* Tab (or ↓) to move focus to the lookup results
* Enter to select "CAPCOM"

## 1.1 Navigation

### 1.1.1 URL entry and quick search

The URL input field can be found in the traditional location in the navigation bar. It can be accessed quickly by pressing ${CTRL+}L. You can then type or paste an URL and press Enter to load the page.

As you enter text in the URL input field, Lagrange starts looking for matches in bookmarks, subscribed feeds, history, identities, and content of cached pages. This provides an easy way to return to a page you've been on recently. Press Tab or ↓ to switch input focus to the results.

Search within cached pages is limited to the (small) set of pages that Lagrange keeps in memory for back navigation. Search terms are case insensitive, and if many words are entered, they are all required to appear in the specified order in any matched content.

Note that the navigation stack is saved to a file when Lagrange is shut down and restored on the next launch. This means the next time you launch Lagrange, you can still search the contents of past pages. However, navigation stacks are tab-specific, so closing a tab will delete its history as well.

You can also make online search queries via the URL input field. When a search URL is configured on the "General" tab of Preferences, text entered in the URL field is passed to the search URL as a query parameter. A search query will only occur when Enter is pressed while the [Search Query] indicator is visible. One way to configure the search URL is to right-click on a search engine's "Search" link — say, when you are on the engine's front page — and select "Use as Search URL" from the context menu.

See section 2.5 about further customizing the search behavior.

### 1.1.2 Links

The type and destination of a link are indicated by the link's icon and color: ➤ links to the same domain, and 🌐 to a different domain. The colors are:

* Blue for Gemini
* Green for Gopher
* Orange for HTTP(S)
* Red for other/unknown/invalid (cannot be opened)

Links colors may change depending on the page color theme. (See section 2.3.1 "Color themes".)

The "Show URL on hover" option can be enabled in Preferences to show additional information when you move the mouse cursor over a link: the destination domain, URL scheme for non-Gemini links, date of the last visit to the URL, and the identity that will be used when opening the link.

If a link would normally use the default ➤ icon but there is an Emoji at the beginning of the link label, that Emoji is used as the link icon instead. In these cases, you can always assume that the link is a Gemini link whose destination is the same domain that you're currently on.

The "Network" tab of Preferences has a few settings that affect the presentation of links and URLs in general:

* "Decode URLs" causes percent-coding to be decoded for the user interface, so one can see international characters in URLs.
* "Maximum URL size" sets a limit for how long URLs can be. While Gemini servers are required to enforce a limit of 1024 bytes for URLs, this setting affects all URLs regardless of scheme. Link lines with URLs longer than this will be presented as plain text.

### 1.1.3 Page caching

When navigating to a new page, the old page is cached in memory. If you navigate back, the cached copy of the old page is restored. Think of it as rewinding time — you return to a past time as if nothing had happened. The same applies to forward navigation; cached pages are loaded if available. This allows back and forward navigation to happen instantly, without any network requests.

The page cache is saved to a file when Lagrange is shut down so it can be restored on the next launch.

Maximum size of the cache can be configured on the "Content" tab of Preferences. Note that the entire cache is kept in memory at runtime. When the cache fills up, the oldest and largest page content is removed — both factors contribute to the removal. You can set the maximum size to 0 to disable caching altogether, but that will also disable the page content quick search feature.

### 1.1.4 Opening links in a new tab

Holding down ${CTRL} when left-clicking on a link causes it to open in a new tab. Alternatively, middle-clicking a link has the same effect.

${SHIFT+}${CTRL+}click opens the link in a new background tab.

Right-clicking on a link shows a link-specific context menu. From there, you can also open the link in a new background tab, which will keep the current tab open.

### 1.1.5 Opening links to the side

Holding down ${SHIFT} when left-clicking on a link opens it in split view mode on the other side of the split. When in split view mode, your tab pinning preference will determine the tab on which clicked links will open. See section 1.9 for more information about split view modes.

### 1.1.6 Opening links using the keyboard

Lagrange has two modes for navigating links with the keyboard. The first uses a modifier key (${ALT} by default): while the modifier is pressed, alphanumeric shortcuts are shown for each visible link in the window. You can then press the corresponding key, still holding the modifier, to open a link. The second mode is based on letters only and focuses on the page row keys. You press and release the activation key ("F" by default) to show the link shortcut letters. In this mode the shortcuts are not in alphabetic order, but instead roughly sorted based on proximity to the F and J keys. You may find this easier to use since it is a simple sequence of key presses without using modifiers, allowing one to keep fingers on or near the home row.

You can give it a try now with the link below. Either hold down ${ALT}, or press and release F.

=> gemini://geminiprotocol.net/ Project Gemini

## 1.2 Tabs

Press ${CTRL+}T to open a new tab, and ${CTRL+}W to close the current tab. Right-clicking on buttons in the tab bar shows a context menu for additional tab-related functions.

The set of open tabs and their full contents are saved when you quit the application and restored when relaunch it.

### 1.2.1 Highlighting of open links

When you open a tab, and the URL of that tab is found in a link on another page, that link will be highlighted. This way you can conveniently see which links are currently open in other tabs. These highlights will assist you in navigating hierarchies and index pages.

### 1.2.2 Auto-reloading

A tab can be set to auto-reload at given intervals. The setting is remembered until the tab is closed. This is helpful if you keep a  periodically updated page open for longer periods of time.

The feature can be found in the page context menu: right-click and select "Tools > Set Auto-Reload...".

## 1.3 Sidebars

The sidebars can be toggled via menus or by pressing ${SHIFT+}${CTRL+}L or ${SHIFT+}${CTRL+}P (for the left/right sidebar, respectively). Both sidebars have five tabs:

* Bookmarks: List of bookmarks that you've created, organized into folders. Bookmarks appear first in search results for quick and easy access.
* Feeds: Entries found on subscribed pages.
* History: Chronological list of visited URLs. This is not a full history of all the URLs you've accessed over time — only unique URLs are shown at the latest access time.
* Identities: TLS client certificates.
* Outline: List of the headings in the currently open tab. Useful when reading longer documents.

${CTRL+}1 through ${CTRL+}5 switch between the left sidebar tabs, or hide the sidebar if the current tab's key is pressed. You can also press Escape to dismiss sidebars.

## 1.4 Bookmarks

Press ${CTRL+}D to bookmark the currently open URL.

Newly added bookmarks appear at the bottom of the Bookmarks sidebar. You can drag and drop items in the list to change their order.

In addition to a title, bookmarks can have tags. Some tags have a special meaning, but you are free to enter whatever you want in the tags field. In quick search results, tags are given extra weight so they appear higher in results.

By default, bookmarks are assigned random icons. You can enter a custom icon for a bookmark in the bookmark edit dialog to make it easier to recognize a particular site at a glance. The icon must be a single Unicode character. It will appear in the bookmark list, tab titles, feed entry list, quick search results, and page top banners.

### 1.4.1 Folders

Press ${SHIFT+}N to create a new bookmark folder. Newly added folders appear in the bottom of the bookmark list.

You can drag and drop bookmarks in and out of folders. Folders can also be nested inside each other. Clicking on a folder heading will toggle its fold state, either hiding or showing its contents. The fold state is remembered across sessions.

You can open all the bookmarks inside a folder in new tabs using the sidebar context menu (right-click on a folder). A new tab is instantly created for each bookmark, including ones in nested subfolders. However, the bookmarked pages will load sequentially to avoid excessive network traffic.

### 1.4.2 Sharing and batch importing

=> about:bookmarks  The special page "about:bookmarks" is used for listing bookmarks in various ways.
It has three different modes that can be opened via menus:

* listing bookmarks alphabetically
* listing bookmarks grouped by tag
* listing bookmarks as a feed with creation dates

The generated page can be saved to Downloads or you can copy all or parts of it to the clipboard. For example, you can then use these listings to share public bookmarks on your capsule.

To import all links on a page as bookmarks, use the page context menu to select "Tools > Import Links as Bookmarks...". You can also right-click on individual links and select "Bookmark Link...".

Importing links on a page will not cause any folders to be (re)created. To fully export and import your bookmarks, tags, custom icons, and folders, see section 1.12.

### 1.4.3 Remote bookmarks

This version of Lagrange does not support automatic bookmark synchronization. By default all bookmarks are stored locally. However, a remote bookmarks feature is provided to allow accessing a set of bookmarks from everywhere. This way you can set up your own centralized bookmark pages or use any public Gemini page as a source of bookmarks.

A local bookmark can be turned into a source of remote bookmarks via the Bookmarks context menu. Right-click the bookmark and select "Use as Remote Source". The ⤓ icon is used to indicate remote items in the Bookmarks list. Remote sources are checked when launching Lagrange and manually with the "Refresh Remote Sources" menu item.

All links found in the remote sources become remote bookmarks and are included in the Bookmarks list. If a URL is already bookmarked locally, any remote bookmarks with a matching URL are not shown.

Note that remote bookmarks are read-only: they cannot be edited or tagged. This means you cannot subscribe to a remote bookmark without first making a local duplicate of it. If you want to make local copies of all the links in the remote source, open the remote source page and use the "Import Links as Bookmarks..." context menu item on it. After refreshing remote sources, the remote copies of the bookmarks will not be shown any more.

### 1.4.4 Behavioral tags

Bookmarks may use a number of special tags that control their behavior. In practice, these are stored in the bookmarks.ini "tags" entries, but are hidden from the Tags field in the app UI.

* A ".homepage" tag makes a bookmark one of the pages that will be opened when pressing the 🏠 button. If multiple bookmarks are tagged as homepages, a random one is selected.
* A ".subscribed" tag means that Lagrange will periodically fetch the bookmarked page and look for Gemini feed links. All the found links that match the required style ("YYYY-MM-DD Entry title") will appear in the Feeds sidebar tab.
* ".headings" can be used together with ".subscribed" to subscribe to new headings instead of Gemini feed links.
* ".ignoreweb" modifies a feed subscription to ignore all HTTP(S) URLs. This is useful if a feed contains both Gemini and web links, but you're only interested in the Gemini ones.
* The ".remotesource" tag marks the bookmark as a source of remote bookmarks. All links on the source pages are shown as remote bookmarks in the Bookmarks list.
* The ".remote" tag is used for remote bookmarks. These bookmarks cannot be edited or tagged, but you can make a local duplicate to turn it into a regular bookmark.
* The ".usericon" tag prevents a random icon to be selected for the bookmark. This tag is automatically applied when an icon character is entered in the bookmark editor.
* The ".linksplit" tag causes all links on the bookmarked page to open to the side, automatically enabling split view mode.

## 1.5 Subscribing to feeds

You may be familiar with XML-based RSS and Atom feeds from the web. The Gemini equivalent of these is Gemini feeds. A Gemini feed is simply a regular 'text/gemini' page that contains one or more links whose labels are formatted in a particular way. This makes it very easy to write pages that clients can subscribe to.
=> gemini://geminiprotocol.net/docs/companion/subscription.gmi  See "Subscribing to Gemini pages" for more information.

Lagrange supports Gemini and Atom feed subscriptions. Atom feeds are automatically translated to the Gemini feed format so they can be viewed and subscribed to like a normal 'text/gemini' page. RSS feeds are not supported.

Subscriptions are managed via bookmarks. When you subscribe to a feed page, a bookmark is created and the special ".subscribed" tag is applied on it. In the Bookmarks list, this is indicated by a ★ icon. There is no other difference between normal bookmarks and feed subscriptions — you may tag any bookmark as a subscription and Lagrange will look through it for feed-style links. The bookmark title is used as the feed title. This defaults to the top heading of the feed index page, but you can edit it to suit your needs.

Feeds are refreshed periodically while Lagrange is running, and also immediately after launching if it has been a while since the previous refresh. You may also manually refresh all feeds via the menus or by pressing ${SHIFT+}${CTRL+}R.

The Feeds sidebar tab displays recent feed entries. From there you can open entries and mark them as read/unread.

To see a list of all entries from all feeds, open the "Feed entries" page. This page also shows how long has it been since the previous feed refresh.
=> about:feeds

## 1.6 Identities (client certificates)

Gemini uses TLS client certificates for user/session identification purposes. Unlike on the web where user identity tracking is covert and automatic, client certificates must be manually taken into use, and you are able to define how long each certificate remains valid. The term "Identity" is used in Lagrange to refer to client certificates.

The Identities sidebar tab shows all identities known to Lagrange. Press ${CTRL+}4 to show it. This includes identities created in Lagrange and any identities based on imported X.509 certificates.

### 1.6.1 Creating a new identity

Click on the 👤 button in the navigation bar and select "New Identity..." or "New Identity for Domain...". The shortcut for this is ${SHIFT+}${CTRL+}N.

Consider any information you enter in the certificate as public — only the Common Name is required to be non-empty. The generated certificate will use the Common Name as the issuer and subject of the certificate, making it clear that the certificate is self-signed. The other required field is the expiration date in "Valid until". Entering a year is sufficient, and means that the certificate is valid until the end of that year.

The "Temporary" option prevents the identity from being saved persistently — it will be deleted as soon as you quit Lagrange. Otherwise, the certificate and its private key are written to .crt and .pem files.

### 1.6.2 Using an identity

You will need to select an identity when you encounter this error message:

> 🔑 Certificate Required

Clicking on an identity in the sidebar shows a menu where you can control usage of the identity for the currently open URL. On subsequent page loads, the certificate will then be sent to the server when the URL or any URL under it is fetched. You can click on the 👤 button in the navigation bar to see which identity is being used for the current page.

As the sidebar is not keyboard-navigable, note that identities can also be accessed via lookup results. Identities matching the search terms are shown as the last category in the lookup results list. From there, one can toggle an identity for the current page, or stop using it on all pages.

Identities may also be used by pinning one to a bookmark. Whenever the bookmark is then opened, the associated identity is taken into use. The identity also gets permanently "pinned" to the opened tab. This means that the tab keeps using the identity for all subsequent requests, but can only switch to URLs inside the same capsule. If a link leads elsewhere, that link gets opened in a new tab with no identity pinned. This way, one can navigate freely inside the capsule while keeping the identity in use, while not accidentally sending it to any other capsule, for example if you forget you are using an identity and manually enter some other capsule's URL. To end use of the identity, it has to be manually unpinned from the tab (via the Identity button in the navbar), or the tab has to be closed. Keeping the pinned identity tab-specific is also useful because then the same URL can be simultaneously opened with several different identities, in separate tabs.

### 1.6.3 Importing existing certificates

To import an existing X.509 certificate as an identity, press ${SHIFT+}${CTRL+}I or click on 👤 and select "Import..." (macOS: Identity menu → Import...).

When the Import Identity dialog opens, it checks the currently open page for any certificates and private keys in PEM format. If found, these are automatically loaded in. You can also press ${CTRL+}V to paste PEM-formatted certificates and/or private keys, or drag-and-drop a PEM-formatted .crt/.key files on the Lagrange window while the dialog is open.

Alternatively, you can manually copy the certificate files so Lagrange can find them. At launch, Lagrange looks through its "idents" directory to see if any new certificates have been copied there. (See "Runtime files" below for the location; it is platform-specific) The file format must be PEM. Both a certificate (.crt) and its private key (.key) must be found in "idents" and they must have matching file names. For example:
* mycert.crt
* mycert.key
Lagrange will add a note to the imported identities to mark them as "Imported".

Note that you can find the certificates of any exported identities inside a user data ZIP archive. See sections 1.12 and 6 for details.

## 1.7 Downloads

Press ${CTRL+}S to save the contents of the current page to the Downloads folder. This works on all pages regardless of whether Lagrange can display the contents or not.

When image or audio content is displayed inline, you can right-click on it and select "Save to Downloads" in the context menu.

The 🔃 button on the right side of the URL input field is the Reload/Stop button — it reloads the current page or stops an ongoing download. During large downloads, an additional progress indicator appears next to the Stop button.

The location where downloaded files are saved can be changed in Preferences. The default location is "Downloads" in your home directory.

## 1.8 Uploads (with Titan)

Titan is a sister protocol to Gemini that enables sending arbitrary amounts of data from a client to a server. The Gemini protocol itself only enables sending up to 1024 bytes of data in a request. Furthermore, the request URL also counts against that limit, and the sent data must be percent-encoded so it can be parsed as a valid URL. Consequently, Gemini clients can only send very limited amounts of data to a server. Titan solves this by expanding the request so that the request URL is followed by a payload field. When it comes to TLS, Titan is equivalent to Gemini, so the same server and client certificates can be used with both.

=> gemini://transjovian.org/titan  Titan Protocol (by Alex Schroeder)

While Titan and Gemini are related, Titan is a separate protocol and regular Gemini servers are not expected to support it. Many services have no need to let clients upload large amounts of data, but it is useful for some specific cases. For example, a server that hosts a gemlog could enable Titan uploads for submitting new posts, or editing existing posts by uploading a revised version.

As far as Lagrange is concerned, Titan is just one of the supported URL schemes. Whenever you try to open a "titan://" URL, no matter if it is manually entered into the URL field, or by clicking on a link, opening a bookmark, feed entry, or via a redirect, a dialog will open where you can enter the data to upload:

* You can type text into the input field on the "Text" tab. It will be sent to the server using 'text/plain' as the media type.
* You can drag and drop a file on the dialog. The details of the file to be uploaded are visible on the "File" tab. The media type can be specified manually if Lagrange does not correctly detect it.

The upload token is a feature of Titan where servers can require a certain token text/passphrase for uploads. It is up to the server how this is interpreted. It could be used as a simple password, or even a command to further instruct the server about what to do with the uploaded data. Please refer to the server's instructions about what to enter here. The token may also be left empty.

Gemtext syntax highlighting is supported in the upload dialog's text field. You can toggle this feature in "Preferences > Appearance". By default, Lagrange comes with a single monospace font, so unless you install additional monospace weights/styles, the syntax highlighting will only use different colors for the Gemtext line types. You can install this fontpack to include bold and italic fonts for the highlighting:
=> gemini://skyjake.fi/fonts/mono/iosevka-term-extended.fontpack  Iosevka Term Extended (7.6 MB)

The text entered into the upload dialog's main text field is protected against accidental closing of the dialog or the application, or a crash. The previous text is restored when the dialog is reopened. The text field contents are only cleared when the submitted Titan request has been successfully completed.

## 1.9 Split view mode

By default, only one tab is visible at a time in the application window. However, sometimes it is beneficial to see two pages at once. For example, many capsules have top-level menus or lists of articles, and keeping the menu/index visible on the side makes navigation less cumbersome.

Split view mode divides the UI into two equivalent parts. You can have multiple tabs open in each split. Closing all tabs on one side will remove the split and return back to the normal unsplit mode.

View splitting is primarily controlled using the view split menu. The default keybinding for showing it is ${CTRL+}J. For convenience it is recommended to use the shortcuts listed in the menu to change split modes. For example, the sequence ${CTRL+}J 2 can be used to quickly activate a 50% horizontal split, and ${CTRL+}J 1 will merge all open tabs back into the normal unsplit view.

Another way to activate split view mode is to click on a link while holding ${SHIFT}.

Each split has its own sidebars, which means that in split view mode you can have a total of four sidebars open at the same time.

### 1.9.1 Switching focus

At any given time, one of the splits has keyboard focus. This is indicated by a colored line at the top of the section, and some UI elements will be dimmed out on the unfocused side.

To switch keyboard focus between the sections, you can use the Next/Previous Tab keybindings or Ctrl+Tab. Next/Previous Tab is particularly convenient as it cycles through all open tabs, jumping to the other side of the split when appropriate.

You may also press Tab to cycle input focus between all the URL input fields.

### 1.9.2 Pinning

While it is sometimes useful to simply have two independent browsers open side by side, by default view splitting is meant to assist in navigating hierarchies and lists. In the typical use case, you'll have a menu or an index page on the left, and a content page open on the right. Links clicked on the left will automatically open on the right.

This is called "pinning" and the behavior can be configured in Preferences. The "Split view pinning" setting on the "General" tab of Preferences controls where links get opened in a split view. There are three modes available:

* "None" causes links to open in the tab where the link is clicked. In this mode, both sides of the split can be navigated independently.
* "Left Tab" causes links clicked on the left tab to open on the right side. The page open in the left tab is therefore "pinned" and does not change unless you enter a new URL or navigate to the parent or root.
* "Right Tab" is the same but works the other way around. The page open in the right tab is pinned and clicked links open on the left.

The default pinning mode is "Left Tab".

The ◧ indicator is shown in the URL input field when the current tab is pinned.

## 1.10 Viewing local files and directories

"file://" URLs can be used for accessing local files and directories. File types known to Lagrange, such as .gmi, .txt., .png, .jpg, and .zip, can be viewed inside the application. In this release, types of local files are detected solely based on the file extension.

When viewing a directory, its contents are shown as a list of links. A similar page is shown when viewing a directory inside a ZIP archive.

Note that ZIP archives are not decompressed while browsing their directory structure. Each request that accesses a compressed file in an archive will cause only that particular file to be decompressed. This may cause slow response times when dealing with large compressed files.

## 1.11 Gempub

Gempub is an e-book/archival format that is essentially a set of Gemtext files stored in a ZIP archive.

=> https://codeberg.org/oppenlab/gempub  Gempub specification

Lagrange can be used as a Gempub reader. When a .gpub file has been saved locally, you can open it in the application to see the book cover page. On the cover page you will find a link that opens the contents of the book. When clicked, split view mode is automatically enabled and both the book index page and the first chapter are shown (unless split view pinning has been disabled).

## 1.12 Input prompt

An input prompt dialog is shown when the server asks for input from the user. Typically, you would enter just a word or two, e.g., the search terms for a search engine. However, input prompts have a few advanced features that can help with more sophisticated use cases.

When entering a longer piece of text, it may help to scale the text a big larger. The font size can be changed with the keys bound to "Zoom In" and "Zoom Out". The width of the dialog can be resized by dragging the left or right edge with a mouse. Both the font size and the dialog width are saved persistently.

The behavior of the Return key can be switched between sending the input to the server and inserting a line break. This can be configured in "Preferences > UI".

The dialog has a context menu for additional functionality. Click on the Ellipsis (⋯) button to open it.

* "Paste Preceding Line" inserts the contents of the Gemtext source line that immediately precedes the link that caused the input prompt to open. This is sometimes used for "Edit" actions in Gemini applications.
* "Assume This URL Requires Input" modifies what happens when the prompt's URL is opened. Normally, it takes two requests to submit input: the first one causes the prompt to open, and the second one sends the user's input to the server. To make this more efficient, you can assume the URL requires input and Lagrange will prompt you automatically before sending anything to the server. (It is possible that some applications may expect the two requests to arrive in a sequence, however usually there are no problems submitting query strings directly.)
* Restoring past entries: The rest of the items in the menu are for input that has been submitted previously. Selecting one will cause it be inserted into the input field.

## 1.13 Export/import user data

The export/import feature allows one to manually export and import identities, bookmarks, text snippets, browsing history, and site-specific information via a ZIP archive.

"User Data > Export" can be found in the File menu or the hamburger menu. In practice, this creates a compressed archive that you can then save to the Downloads folder or open in an external application. From there, you can transfer the archive manually onto another device, or just put in a safe place for backup.

Opening the exported archive works similar to fontpacks (see section 2.4): when viewing the ZIP in the app, there is a button in the bottom of the window to import the contained data. Fine-grained controls are provided to choose which data gets imported and how, so you don't have to overwrite all the existing data.

Note that browsing history also contains the read status of feed entries, because those are tracked based on whether entry URLs have been visited. This means a transfer of user data includes the up-to-date status of each subscription as well.

There is no automatic sync service to share user data between multiple devices.

# 2 Customization

You can find a number of settings in Preferences to customize the user interface and page contents.

## 2.1 Browsing behavior

On the "General" tab, "Split view pinning" controls which tab links will be opened on when browsing in split view mode. The default mode is "Left Tab", which means that the page in the left tab is pinned (remains unchanged) when clicking on a link. For more information, see section 1.9.

On the "Content" tab, the "Open images in Data URLs" option determines if image data embedded into links using data URLs is automatically shown after the page has finished loading. This only applies to a handful of common image media types: JPEG, PNG, GIF, and WebP. Note that the maximum size of an URL has a limit, so these embedded images have to fit under the configured limit to be recognized as valid links. Image from data URLs are displayed as links' inline content, just like with any other URL scheme.

The "Open index.gmi in ZIP archives" option controls whether index.gmi pages are automatically opened while browsing the contents of a ZIP archive. The purpose is to simulate the behavior of a Gemini server where opening a directory will by default show its index page. Enabling this option makes navigating an archived copy of a capsule a more streamlined experience.

One important characteristic of Gemini is that you remain in control of what gets loaded and when. The browser will not suddenly fetch a ton of images, autoplay videos, or make surreptitious connections to any tracking servers — each network request is purposeful and manually triggered. With this in mind, the "Load next image on scroll key" option on the "UI" tab is provided to assist keyboard-only browsing and to facilitate a focused reading experience. When enabled, if there is an image link visible on the page and you press Space or ↓ (or whichever keys are bound to the scroll actions), it will be loaded and shown inline _instead_ of the view scrolling down. This allows you to read and see all the content of the page while only tapping on a single key on the keyboard.

## 2.2 UI appearance

There are four different color schemes for the UI: two for dark mode, and two for light mode. These can be selected on the "Appearance" tab of the Preferences dialog:

* Dark mode: "Black" and "Dark" have a fully black or dark gray UI.
* Light mode: "White" and "Light" have completety white or light gray UI.

On macOS, Lagrange will automatically switch between dark and light modes if the "Use system theme" setting is enabled. On other platforms you'll need to switch manually.

On Windows, an option is provided to use a custom window frame. This provides a more consistent visual style for the application. However, the custom frame overrides default behaviors of the window, so if you are a Windows power user expect it to not support all the special interactions. For example, when pressing the Windows+Left/Right key, the window is resized to take over one half of the screen. Normally, Windows would then prompt to select another window to fill the rest of the screen, but this does not happen with the custom window frame.

## 2.3 Page style and layout

The "Page Style" and "Page Layout" tabs of the Preferences dialog let you customize the appearance and arrangement of page contents.

### 2.3.1 Color themes

Page content color themes are selected on the "Page Style" tab of Preferences. The "Dark theme" is active in dark UI mode, and the "Light theme" is active in light UI mode.

* Colorful Dark: All elements of the page are colored; the background is dark and text is light. This mode provides the best visual distinction between different domains because more color combinations are available.
* Colorful Light: A single, bright background color with black text. This is the most colorful light theme. Note that colored backgrounds may reduce readability.
* Black: Gray body text and brightly colored headings on a black background.
* Gray: Slightly brighter version of Black, i.e., gray body text and colored headings on a gray background.
* White: Colored headings on a white background.
* Sepia: Light sepia background with black text. Does not change depending on domain; use this for readability if you prefer a sepia reading experience.
* Oceanic: Mostly teal/blue theme with a few orange/red accents. Brightness and saturation vary randomly based on domain.
* High Contrast: White background with black text. Does not change depending on domain; use this for readability if you prefer maximum contrast between text and the background.

The "Saturation" setting can be used to tone down the theme colors for a more neutral appearance.

### 2.3.2 Site-specific colors

You can manually customize the color theme of a site. Open "Page Information" and click on "Settings" to open the Site-Specific Settings dialog. The default keyboard shortcut for this is ${SHIFT+}${CTRL+}Comma.

The "Theme palette seed" is the input data given to the theme generator that determines a site's color palette. The theme generator is designed to algorithmically choose a palette whose colors go together. It is not possible to individually pick the colors of a theme.

You can enter any text as the palette seed. By default, the seed is the site's hostname, or a user name found in the URL path (e.g., "gemini://example.com/~User/" → seed "User"). Examples of how to use this:

* Enter a word or phrase, or just random characters, to find a theme that you like.
* To copy the theme of another site, enter the hostname of that site as the seed.

### 2.3.3 Text styling

The fonts for document headings, body text, and preformatted blocks can be chosen separately. There is also a separate font for monospaced body text that is used when the Gemini/Gopher-specific "Monospace body" option is enabled. See section 2.4 for more details about using fonts.

The "Bold links" option determines whether links use a bold font. Enabling "Visited" means that the bold font is used also for visited links, not just unvisited ones. "On Dark" and "On Light" enable bold links on a dark/light background. For readability, using bold fonts on a light background is recommended because differences in text color and link icon color are less noticeable.

### 2.3.4 Layout options

Paragraph layout options:

* Line width: This setting determines the maximum width for text lines. "Fill" disables the maximum limit and fits text lines to the full width of the window. (Shorter lines are generally easier to read.)
* Line spacing: Adjust spacing between text lines. A value of 1.1 would add 10% more space, while 2.0 would mean there is a full-height empty line between all text lines. For the best results, keep this pretty close to 1.0. (Values smaller than 1.0 may lead to visual artifacts as lines become overlapped.)
* Tab width: Number of spaces to use for tab stops.
* Justify: Paragraphs are justified when they at least three lines long. Spaces on each line are expanded to equalize line widths.
* Big 1st paragraph: When enabled, the leading paragraph on the page is shown in a slightly larger font. (The leading paragraph is autodetected by Lagrange, so it is not guaranteed to always be appropriately chosen.)

Other layout options:

* Quote indicator: Quoted text is shown in an italic font. Additionally, you can select between a quotation mark icon and the traditional vertical line along the left edge of the quote.
* Capsule icon on left side: When the window is wide enough, show the capsule icon on the left side of the page at a fixed position together with the current level 1 heading.
* Collapse preformatted: After loading a page, immediately hide all preformatted blocks, showing only the alt texts.

## 2.4 Fonts

This version of Lagrange supports TrueType fonts. To use a new font, simply view a .ttf file in the app and a page footer action is available for performing the installation. For example, try drag-and-dropping a .ttf file on the window. Alternatively, you can manually copy the font to the "fonts" subdirectory of the user-specific configuration directory (see section 3.5).

The "Page Style" tab of the Preferences dialog contains options that affect the appearance of text in page content. The user interface font can be changed in the "Appearance" tab, along with other text renderer settings.

To be precise, on the "Page Style" tab you can select which _typefaces_ to use for certain elements of the page; picking a particular font (including its size, weight, style, etc.) for specific elements is not possible. Lagrange controls the size and styling of text by choosing fonts according to your theme and typeface preferences. The term "font" is often used to mean "typeface" in this document and in the app UI.

There are three built-in fonts available:

* "Roboto" is the default UI font that is also used for page content.
* "Source Sans" is the previous default font. It has more personality than Roboto, but rarely matches the system fonts.
* "Iosevka" is the monospaced font.

There is also an "Iosevka (compact)" variant that actually uses the font's original line spacing. It is the default for preformatted blocks to avoid gaps between lines of ASCII art, but not for body text for better legibility.

See sections 2.4.4 and 5 for more details about font management, compatibility, and configuration.

### 2.4.1 Monospace body

The "Monospace body" option causes all pages to be displayed in a monospace font. For example, most Gopher content has been written with the assumption of a monospace font, so it may provide a better reading experience to enable this for Gopher pages. The selected "Monospace font" is applied to the entire document.

Handling of whitespace in page content also changes when this option is enabled: spaces are no longer normalized so if the source uses multiple spaces somewhere, those are shown as-is.

### 2.4.2 ANSI escapes

=> https://en.wikipedia.org/wiki/ANSI_escape_code  ANSI escape code (Wikipedia):
> ANSI escape sequences are a standard for in-band signaling to control cursor location, color, font styling, and other options on video text terminals and terminal emulators.

Sometimes these codes are used for things like colored ASCII art. However, Lagrange is not a terminal emulator so only a very minimal set of codes have any effect; the rest are ignored.

The "ANSI escapes" setting controls which ANSI escape codes are enabled:

* "FG Color" enables changes to text foreground color.
* "BG Color" enables changes to text background color.
* "Font Style" enables changing the font style: bold, light, italic, regular, or monospace. (These correspond to codes 1, 2, 3, 10, and 11.)

A warning banner is displayed if any codes are detected on a page. This helps you be aware of potential visual artifacts, like text color that is being forced to black regardless of the page background color. Click on the warning to dismiss it on a per-site basis.

If you serve content via Gemini, please be aware that ANSI escapes may not be supported by clients, and may in fact disrupt the behavior of a client in unexpected ways. For instance, consider a screen reader or a web proxy that doesn't filter out the codes. Only employ ANSI escapes when the user has somehow indicated that is their preference.

### 2.4.3 Other font options

On the "Content" tab, the "Font glyph warnings" option controls whether a warning will be shown when a page is missing one or more characters. This is typically due to the page being in a language that is not covered by any of the installed fonts. Clicking on the glyph warning banner opens the font management page.

On the "Appearance" tab, "Font smoothing" enables or disables glyph antialiasing. In this version, it is recommended that smoothing is always enabled. This is because the text renderer does not support hinting of any kind, which means that without smoothing, glyph shapes will be severely distorted. You may still want to try disabling this option if antialiasing causes eye strain for you, or you are using a special font that is designed to not be smoothed.

### 2.4.4 Managing fonts

Open "about:fonts" to see all the installed fonts, and enable, disable or uninstall individual fontpacks. At the top of the page, there is a link to the skyjake.fi Font Library that contains a curated collection of fontpacks that can be freely distributed. From there you can conveniently install more fonts specifically tuned for Lagrange.

The rest of the page is divided to two sections: enabled and disabled fontpacks. Individual packs can be disabled, so they remain installed but not in use. (Tip: Use the Outline sidebar to see a list of all packs, if there are many.)

Click on the "View file" links to see what each fontpack contains. The fontpack format is described in section 5: it is simply a ZIP archive with some metadata and a bunch of font files. When you install a TrueType font (i.e., copy it to the user's fonts directory), it is treated as a fontpack containing a single file, although no ZIP archive is created for it. Use the "View fontpack.ini template" link to see the generated metadata that can be used as a basis for creating an actual fontpack.

There are multiple locations where Lagrange looks for fontpacks at launch:

* Directory containing the app binary (BIN_DIR)
* (BIN_DIR)/fonts
* (BIN_DIR)/../share/lagrange
* (BIN_DIR)/../../share/lagrange
* macOS: Lagrange.app/Contents/Resources
* User configuration directory (CFG_DIR; see section 3.5)
* (CFG_DIR)/fonts

Individual TrueType fonts are automatically loaded only from the last one, (CFG_DIR)/fonts.

If a "fonts.ini" file is present in the user configuration directory, it will be loaded as fontpack metadata (see section 5). This way you can manually configure fonts without creating a ZIP archive. For example:

```fonts.ini example
[couriercode]
name = "Courier Code"
regular = "/home/jaakko/Fonts/Courier Code/CourierCode-Roman.ttf"
glyphscale = 0.85
monospace = true
```

About compatibility: fonts are complex, and while the TrueType format is not the most advanced one, it still has features that are not supported in Lagrange. The technical reason is that glyphs are rasterized using stb_truetype, a rather simple TrueType font library. (It's nice and small, though.) You may find that some fonts simply fail to load correctly, or look wrong in the app.

* Hinting is not supported.
* Bitmap glyphs are not supported.
* Multi-color glyphs are not supported.

TrueType Collections (.ttc) can be used, with the restriction that each declared font uses a single index from the collection. The index must be appended to the file name:
```.ttc example
regular = "NotoSansCJK-Regular.ttc:2"
```

## 2.5 Text snippets and custom queries

Gemlogs are often written entirely manually, so you may find yourself typing or copy-pasting the same headers, footers, or other small snippets into each post. You may also need to repeatedly enter specific pieces of text in a game or another interactive capsule. On desktop operating systems, there are multiple existing utilities that facilitate these use cases. While you may be able to use these with Lagrange, the app also has a built-in text snippet manager that works on any platform.

In "Preferences > Snippets", you can define a set of text snippets that can be pasted into any input field via the field's context menu. Snippets can also be created by right-clicking on a link or selected text on a page.

Text snippets whose name begins with an exclamation point ("bang") have a special meaning: they are used for additional search query URLs. For example, if the snippet "!w" is defined as "gemini://gemi.dev/cgi-bin/wp.cgi/search", you can then enter the following in the navbar URL field to make a search on Gemipedia:
```
!w Gemini Protocol
```
The additional words following the "!w" bang snippet are appended as a query string to the URL expanded from the snippet. This way, you can configure any number of searches or other shortcuts that take input. Bang snippet names can be longer than a single character but they cannot contain spaces.

The keybinding ${SHIFT+}1 ("Enter a snippet query") focuses the URL field and inserts the leading '!' character so you can save a few keystrokes when using query snippets.

## 2.6 Proxies

Gemini allows relaying requests via a proxy server. On the "Network" tab, you can configure proxy servers for Gemini, Gopher, and HTTP/HTTPS requests.

When an HTTP proxy server is configured, HTTP/HTTPS links will no longer open in the system's default web browser but will be loaded via the proxy, expecting it to serve a 'text/gemini' version of the link contents.

## 2.7 URL handling

The "Network" tab of Preferences has a few options related to handling URLs.

Enabling the "Decode URLs" option causes all percent-encoded URLs to be shown in decoded form in the UI. Enabling this option is useful when encountering URLs that contain characters outside the basic Latin (A-Z) alphabet. This does not affect what gets sent to a server when loading pages: Gemini requests are always required to be sent in encoded form.

The "Maximum URL size" setting defines what is considered a valid link in Gemtext. Link lines with URLs longer than this are not considered to be links and are displayed like regular text lines. This only affects links that don't use the "gemini" scheme. The maximum size of a Gemini URL is 1024 bytes.

Having a length limit is necessary due the special case of Data URLs:
=> https://datatracker.ietf.org/doc/html/rfc2397  RFC 2397: The "data" URL scheme
With Data URLs, one is able to embed arbitrary data into a Gemtext file using link lines. This makes it possible to circumvent the intentional limitations of Gemini and override the clients' ability to choose which linked resources should be loaded and when. Without a limit, a server could for example send an arbitrarily large image attachment as part of the page, with no regard to the user's or client's preferences or abilities to view images. Also note that like any non-Gemini scheme, "data" is not expected to be supported by Gemini clients.

## 2.8 Keybindings

The "Keys" tab lets you change which keys are bound to UI commands. Click on an item with the mouse and then press the new key combination that you want bound to it. Right-click on a binding to erase it or reset it to the default.

Erasing a binding can be useful to disable certain features. For example, if you have no use for keyboard navigation of links via a modifier key, that binding can be erased and use of the modifier key for other purposes will no longer distract you by showing the link shortcuts.

To reset all bindings to their defaults, quit Lagrange and delete the "bindings.txt" file in Lagrange's runtime directory. This is a platform-dependent location; see below for more information (under "Runtime files").

## 2.9 Gopher

Lagrange converts Gopher menus to Gemtext for presentation. There are a couple of settings that control the conversion.

On the "Content" tab, the "Autodetect Gopher menu styling" option controls whether Gopher menus should use autodetected Gemtext styling. By default, the app's Gopher experience mimics that of Gemini, where preformatted ASCII art is in separate blocks and paragraph text has its own (variable-width) font. However, the autodetection does not always get it right. Menus with meticulously crafted ASCII may sometimes be misinterpreted. Disabling the style autodetection makes all text lines equal in appearance.

Enabling monospace body text for Gopher (in the "Page Style" tab) will faithfully present the Gopher source text, with original whitespaces intact, while also using the chosen monospace font for all text.

# 3 OS integration

## 3.1 Command line options

Here are some of the commonly needed command line options. Check the "lagrange.1" manual page or the output of --help for a more complete listing.

### URLs/paths
URLs and file paths on the command line are opened after Lagrange has launched. If more than one URL is given, multiple tabs will be opened. For example:
```
$ lagrange gemini://geminiprotocol.net/
```

### --dump
Instead of opening the GUI, fetch each of the URLs/paths specified on the command line and print them to stdout. Metadata about the response will be printed to stderr.

### -E, --echo
Debugging utility: internal events are printed to stdout.

### --help
Print a list of all the available options.

### --sw
Disable hardware accelerated graphics. Note that software rendering is anyway used as a fallback, so usually this option should not be necessary.

### -V, --version
Print the application version.

## 3.2 Opening Gemini links

On macOS and Windows, Lagrange registers itself as a "gemini" URL scheme handler, so you can click on Gemini links in any application to open Lagrange with that URL.

Likewise (on macOS), .gmi/.gemini file extensions are registered as file formats that Lagrange can view so Finder will know how to open those automatically using Lagrange.

## 3.3 Drag and drop

You can drag and drop .gmi files on the Lagrange window to open them in the current tab. Dropping multiple files opens them in separate tabs. This is the recommended way to view local files, because there is no "Open File" menu item. You may also type "file://" URLs in the URL field.

## 3.4 Controlling a running instance

Only one instance of the application is allowed to run at once. This is because each instance uses the same runtime files (section 3.5) without any synchronization. A second instance of the application would overwrite any changes made by the first one, leading to lost bookmarks and other state.

If there already is a running instance you can still use the command line to interact with it: you can open and close tabs, change the currently open URL, or list all the open URLs. See --help for a list of the available options.

## 3.5 Runtime files

The location of user data files can be changed with the --user option. By default, Lagrange stores user-specific persistent files in one of the following locations (depending on the operating system):

```Location of user-specific files on different operating systems (table)
   Windows : C:\Users\Name\AppData\Roaming\fi.skyjake.Lagrange
     macOS : ~/Library/Application Support/fi.skyjake.Lagrange/
Other Unix : ~/.config/lagrange/
```

### bindings.txt
Each line specifies one keybinding:
> {binding-id} {keycode} {flags}
* Binding IDs are defined in src/ui/keys.c.
* Keycode is one of the SDLK constants from SDL (hexadecimal).
* Flags specifies the modifier keys:
```Table of modifier key flags
s : Shift
a : Alt
c : Ctrl
g : Gui (Windows/Command/Meta key)
k : Caps Lock
```

### bookmarks.ini
This file stores all bookmarks and bookmark folders. The format is a subset of TOML: the only supported value types are strings and integers.
```Example bookmark
[51]
url = "gemini://geminiprotocol.net/"
title = "Project Gemini"
tags = ""
icon = 0x264a
created = 1609936844  # 2021-01-06
parent = 99
order = 288
```
* The table name (51) is the unique identifier of the bookmark.
* "url", "title", and "tags" are used as-is. C-style backslash escapes must be used for quotes (for example: \"), and may optionally be used for Unicode characters as well.
* "icon" is a UTF-32 codepoint as a hexadecimal number.
* "created" is a UNIX timestamp for when the bookmark was created. Following the timestamp, a human-readable date is also provided but it is just a comment — that part will be ignored when parsing the file.
* "parent" is the ID of the parent folder. Folders are stored as similar bookmark entries, but their URL value is always an empty string.
* "order" is for sorting the bookmarks list. The list is sorted by ascending order. This value is updated automatically when bookmarks are reordered in the sidebar.

### feeds.txt
Cached state of feed subscriptions. The file may be deleted while the application is not running to force a reset of feed contents. Subscriptions themselves are tracked via bookmark tags so deleting the file does not affect which pages are subscribed.

The file has three sections. The first one is simply a UNIX timestamp indicating when feeds were last refreshed. The second section begins after the comment:
```
# Feeds
```
In this section, each line identifies a subscription so it can be referenced in the feed entries:
> {feed-id} {feed-url}
* The feed ID a hexadecimal number and always eight characters long.

The third section contains all the discovered feed entries. It begins after the comment:
```
# Entries
```
Each feed entry consists of five consecutive lines:
> {feed-id}
> {posted-time}
> {discovery-time}
> {url}
> {title}
* The feed ID is one of the identifiers from the Feeds section (without zeroes for padding).
* The posted time is a UNIX timestamp that specifies when the entry was posted. This is determined from the "YYYY-MM-DD" date found on the link line. If this is a "new headings" subscription, the posted time and the discovery time are the same.
* The discovery time is a UNIX timestamp that marks when the entry was added to the cache.

### fonts.ini
This file is loaded as fontpack metadata (see section 5). It must be manually created.

### idents.lgr and idents/
idents.lgr is a binary file that contains metadata about the client certificates known to the application, for example on which URLs a particular certificate should be active.

The "idents" subdirectory is where the actual client certificates are stored. Each certificate comprises a .crt and a .key file in PEM format. Certificates generated inside the application use the certificate fingerprint as the file name.

### modmap.txt
Translation table for keyboard modifiers. For example, one could swap the Alt and Ctrl keys by changing their mappings. See the comment in the file that explains the format and usage.

### mimehooks.txt
See section 4.

### palette.txt
Palette for UI color themes. This configuration file does not exist by default and must be created manually.

The actual colors used in the user interface are derived from the base palette. Therefore, you should not change the colors too drastically, but instead follow the expected pattern: a range of 5 intensities (black-white), followed by two accent color pairs (dim, bright). The last five colors are reserved for certain specific uses, e.g., the green is used for the navbar lock icon to indicate a trusted server certificate. The palettes defined here do not affect page color themes, only the UI. Note that link icons are considered part of the UI, so you may find that changing the palette will reduce visibility of the icons with some of the page color themes.

The file specifies two palettes: one for dark mode and one for light mode. The current palette is selected with the lines:
```
# Dark
```
and
```
# Light
```

The other lines specify colors:
> {label}: {rgb-hex}
> {label}: {red} {green} {blue}
* {rgb-hex} must use the form "#RRGGBB"
* {red}, {green}, {blue} are decimal numbers in the range 0...255

The configuration below defines the built-in default palette:
```palette.txt with the default UI palette
# Dark

black:      #000000
gray25:     #282828
gray50:     #505050
gray75:     #A0A0A0
white:      #FFFFFF
brown:      106     80      0
orange:     255     192     0
teal:       0       96      128
cyan:       0       192     255
yellow:     255     255     32
red:        255     64      64
magenta:    255     0       255
blue:       132     132     255
green:      0       200     0

# Light

black:      0       0       0
gray25:     75      75      75
gray50:     150     150     150
gray75:     235     235     235
white:      255     255     255
brown:      210     120      10
orange:     235     215     200
teal:       10      110     130
cyan:       170     215     220
yellow:     255     255     32
red:        255     64      64
magenta:    255     0       255
blue:       132     132     255
green:      0       150     0
```

### prefs.cfg
Persistent configuration variables. The file is rewritten when the application is closed. Each line is interpreted as an internal UI event like those printed with the --echo command line option.

### state.lgr
A binary file that contains the current state of the application: open tabs and their scroll positions, and navigation history with cached page content (up to the configured cache limit). You may delete this file when the application is not running to close all tabs and clear the page content cache.

### sitespec.ini
Site-specific settings.

### trusted.2.txt
Trusted server certificates. Each line specifies the certificate fingerprint of one server:
> {domain};{port} {valid-until} {fingerprint}
* Domain names are stored in punycode format if they contain non-ASCII characters.
* The "valid until" expiration date is a UNIX timestamp.
* The fingerprint is an SHA256 checksum of the server certificate's public key in DER format.

### uploadbackup.txt
Backup of the text entered into the Upload with Titan dialog.

### uploadtoken.txt
Backup of the server token.

### visited.2.txt
The combined navigation history of all tabs. Each line specifies one URL:
> {last-visited} {flags} {url}
* The last visited time is stored as a UNIX timestamp.
* Flags is always four bytes long:
```URL flags (table)
0000 : No flags set
0001 : Transient
0002 : Kept
```
The Transient flag is used to indicate redirections and for marking feed entries as read without actually visiting the URL. URLs with the Transient flag do not appear in the History sidebar tab.

The Kept flag is used for preventing the URL from being discarded due to old age. Normally URLs in the navigation history become stale after several months and are removed from the file.

## 3.6 Environment variables

### LAGRANGE_OVERRIDE_DPI
Override display DPI detection with a user-provided value. The same value is applied to all displays. This is useful if your display's DPI value is not being detected correctly. Example:
```96 is the default DPI value
LAGRANGE_OVERRIDE_DPI=96
```

# 4 MIME hooks

MIME hooks enable piping Gemini responses through external programs for arbitrary processing. This allows leveraging scripting languages and binary executables to perform format conversions, content transformation, and data analysis.

Hooks are configured using the file "mimehooks.txt" in Lagrange's config directory. Each hook has a regexp that is matched against the response MIME type and parameters, and each matching hook is offered the response body via stdin. The called external programs are free to rewrite the entire response, including the MIME type. If one of the hooks returns a valid response, it is used as the final response of the Gemini request.

Example use cases:
* Parsing an Atom XML feed and generating a Gemini feed index page
* Rendering a MIDI file using Timidity as PCM WAV
* Generate a graph PNG based on values in a CSV
* Converting HTML or Markdown to 'text/gemini'
* Language translations

## 4.1 Interface

When a hook is called, it is given the MIME type and parameters via command line arguments. The response body is provided via stdin. The request's URL is available in the REQUEST_URL environment variable.

The MIME type and parameters are split at semicolons, so "text/gemini; lang=ja" would be called as:
```
hookprogram text/gemini lang=ja
```

Output from the program (via stdout) must be a valid "20" Gemini response that includes the new MIME type:
```
20 text/gemini; lang=en\r\n
{...body...}
```

Any output that does not follow this format is considered to mean that the hook refused to process the contents. The next hook will be offered the response instead.

## 4.2 mimehooks.txt syntax

Like other Lagrange configuration lines, mimehooks.txt has a simple line-oriented syntax. Lagrange must be restarted for changes to the configuration file to take effect.

Each hook is specified as three lines:
* A human-readable label (for reporting to the user)
* MIME type/parameter regular expression
* Command to execute, plus additional arguments each separated with semicolons

For example:
```mimehooks.txt
Convert Atom to Gemini feed
application/xml
/usr/bin/python3;/home/jaakko/atomconv.py
```

The hook program is executed directly without involving the shell. This means scripts must be invoked via the interpreter executable.

## 4.3 Example: Converting from Atom to Gemini

The following simple Python script demonstrates how a MIME hook could be used to parse an Atom XML document using Python 3 and output a Gemini feed index page based on the parsed entries. This is just a simple example; a more robust script could include more content from the Atom feed and handle errors, too.
```python
import sys
import xml.etree.ElementTree as ET

def atomtag(n):
    return '{http://www.w3.org/2005/Atom}' + n

root = ET.fromstring(sys.stdin.read())
if root.tag != atomtag('feed'):
    sys.exit(0)
feed_title = ''
feed_author = ''
feed_entries = []
for child in root:
    if child.tag == atomtag('title'):
        feed_title = child.text
    elif child.tag == atomtag('entry'):
        feed_entries.append(child)
print("20 text/gemini\r")
print(f'# {feed_title}')
for entry in feed_entries:
    entry_date = ''
    entry_title = ''
    entry_link = ''
    for child in entry:
        if child.tag == atomtag('updated'):
            entry_date = child.text[:10]
        elif child.tag == atomtag('title'):
            entry_title = child.text
        elif child.tag == atomtag('link'):
            entry_link = child.attrib['href']
    print(f'=> {entry_link} {entry_date} {entry_title}')
```

# 5 Fontpacks

Fontpack is a file format defined by Lagrange that is used to combine a set of font files with configuration metadata. The (unregistered) media type for .fontpack files is 'application/lagrange-fontpack+zip'.

A fontpack is a ZIP archive that must have a "fontpack.ini" file at the root level.

```fontpack.ini from firasans.fontpack
version = 1

[firasans]
name        = "Fira Sans"
glyphscale  = 0.85
regular     = "FiraSans-Regular.ttf"
italic      = "FiraSans-Italic.ttf"
light       = "FiraSans-Light.ttf"
semibold    = "FiraSans-SemiBold.ttf"
bold        = "FiraSans-Bold.ttf"
```

Fontpacks may use the Deflate compression method, but that can slow down launching the app because each font must then be decompressed before loading. Therefore, it is recommended to use the -0 (--compression-method store) option when creating the archive. You may also find the -j (--junk-paths) option helpful if the current working directory is not the one where fontpack.ini is located.

Each fontpack has an ID that comes from the file name: the ID of "firasans.fontpack" would be "firasans". Space characters are not allowed in the ID.

Fontpacks are versioned, i.e., they have a version number in their metadata. This makes it possible to tell when a fontpack is an updated version of an existing one. The fontpack ID (file name) must remain the same, though, regardless of the version number.

The "fontpack.ini" file uses TOML syntax and can specify any number of typefaces. In the example above, the line `[firasans]` begins the definition of a typeface called "firasans". If the same typeface is found in multiple fontpacks, only the first one that gets loaded is used; the rest are ignored. Typeface IDs can be the same or different than fontpack IDs; they exist in different namespaces. The typeface ID is what is actually used in "prefs.cfg" to save your font preferences.

## 5.1 Fontpack properties

`version` defines the version number of the fontpack. It is a single integer, and if omitted, defaults to zero. It has no specific meaning except that larger values are considered newer versions.

## 5.2 Typeface properties

### 5.2.1 General
* `name` (string) is the human-readable name of the typeface. This is used in the Preferences dialog and elsewhere in the UI.

### 5.2.2 Prioritization and exclusion
The same character's glyph(s) may be found in several fonts, so a prioritization is applied to pick the most appropriate font. Font selection may also depend on the context, for example preformatted blocks must be displayed using monospace fonts. These properties control when and if the typeface will be used.

* `priority` (integer) defines a sort order for typefaces. The ones with the highest priority are checked first.
* `override` (bool): whether this typeface is always checked first before any other one, in any context. Only one typeface can use this flag.
* `monospace` (bool): is this a monospace typeface and therefore suitable for preformatted blocks and monospace body text.
* `auxiliary` (bool): if true, this typeface is not included in Preferences as a font choice, but is still checked for glyphs if other fonts do not provide them. Suitable for miscellaneous symbols or additional languages, for examples.
* `allowspace` (bool): if true, an auxiliary font's metrics for space characters are used. Sometimes symbol fonts have extra wide spaces, so for example a space next to an Emoji would be too wide. This has no effect for non-auxiliary typefaces.

### 5.2.3 Metrics
These properties can be used to modify the height and spacing of the font.

* `height` (float) is a multiplier to alter the height of the font. It can be at most 2.0, to double the height. This simply scales the font smaller or larger without altering spacing.
* `glyphscale` (float) scales glyphs smaller without changing the height of the font. The value must be 1.0 or smaller. In effect, this lets you increase the spacing between consecutive lines of text. It can be combined with `height` to keep glyphs the same size but just increase line spacing. For example, `glyphscale` 0.833 would counter the scaling caused by `height` 1.2, increasing line spacing by 1.2x.
* `voffset` (float) is multiplier applied to the vertical offset that normally centers scaled glyphs on the line. This allows fine-tuning where the baseline of scaled glyphs ends up. Setting this to 1.0 means that glyphs are vertically centered after scaling with `glyphscale`; 0.0 would disable the centering. Reasonable values are likely in the 0.5…1.5 range, depending on the amount of scaling.

Changing only the `glyphscale` property is the recommended way to alter line spacing. This makes it easier to mix and match fonts on a single line without having to deal with changes in text height. Compare your adjusted scaling to see if it looks suitable next to normal body text.

Each of these properties can be set separately for UI text and page content by using the prefixes `ui.` and `doc.`. For example, to only scale the font when used in the UI, set `ui.height` instead of `height`.

### 5.2.4 Font files
A single typeface can use up to five font files.

* `regular` (string): path of a font file for the regular style. A relative path means that the file is loaded from inside the fontpack archive. Absolute paths can be used to refer to files on the local system.
* `italic` (string): path of a font file for the italic style.
* `light` (string): path of a font file for the light weight.
* `semibold` (string): path of a font file for the semibold weight.
* `bold` (string): path of a font file for the bold weight.

Only the regular style is required. Undefined styles fall back to the closest available style. The same file path can be used in multiple styles; only one copy of the file will be loaded to memory.

When the path refers to a TrueType Collection (.ttc), the font index to use must be appended to the file name:
```.ttc example
regular = "NotoSansCJK-Regular.ttc:2"
```

# 6 User data archives

Lagrange user data archives are compressed ZIP archives that contain browsing history, identities, bookmarks, text snippets, site-specific settings, and/or trusted server certificate fingerprints.

An export archive largely mirrors the contents of the runtime directory (section 3.5). However, the "lagrange-export.ini" metadata file must also be present:

```lagrange-export.ini
# Lagrange user data exported on 2022-04-01 13:34
version = "1.12.0"
timestamp = 1648809264
```
* `version` (string): Version of the app that generated the archive.
* `timestamp` (integer): Time of generation as a UNIX timestamp.

# 7 Misfin

Misfin is a messaging protocol that has been in the works since May 2023. Like Gemini, it relies on TLS and simple text-based requests, with 'text/gemini' as the content format.

Lagrange has supported Misfin since version 1.18. You can import Misfin identity certificates and send messages using them. You will still need a Misfin mailbox where you can receive messages — servers are expected to verify the identity of unknown senders by checking if the sender's certificate matches the one provided by their server. 

A Misfin identity certificate is a TLS client certificate where:

* UID field specifies the mailbox name
* subject alternative name(s) specify the domain name(s)
* Common Name is the human-readable name

You will need to import one or more of these before sending any messages.

When sending a message, the Upload dialog opens in Misfin mode with "To" and "From" fields. As usual, the text editor in the dialog has basic Gemtext syntax highlighting, but otherwise the editor has nothing Misfin-specific. A toggle is provided if you want to send a copy of the message to yourself. Lagrange does not keep copies of sent messages because it does not maintain a local Misfin mailbox.

When you click on a link with a "misfin://" URI, the dialog opens automatically with the recipient address prefilled.

=> gemini://satch.xyz/misfin/  Misfin specification(s) and resources
=> gemini://misfin.org/  Original Misfin specification
=> gemini://bbs.geminispace.org/s/misfin  s/Misfin on BBS

# Open source licenses

=> about:license
